The present invention relates to novel aromatic isocyanates obtained by partially hydrogenating naphthalene as well as the processes for preparing the same, and to their use as an isocyanate component in the production of polyurethanes.
Among the organic polyisocyanates of commercial and economic significance as starting materials for polyurethanes, both rigid and flexible foams, in particular flexible foams, mixtures of diphenylmethane diisocyanate (MDI), polyphenylene polymethylene polyisocyanates, prepolymers based on such materials, and toluene diisocyanate (TDI) are known to be suitable for preparing flexible foams. See, for example, U.S. Pat. Nos. 4,239,856, 4,256,849, 4,261,852 and 4,365,025, 5,070,114, 4,478,960, 4,945,117, 5,369,138, 4,876,292, 5,521,225.
Allophanate modified isocyanates are also known in the art. Various isocyanates containing allophanate groups and processes for their production are disclosed in, for example, U.S. Pat. Nos. 4,738,991, 4,866,103, 5,319,053 and 5,319,054, and European Patents 0,031,650 and 0,393,903.
An improved isocyanate was required to have improved physical properties over TDI, so it needed to be liquid (an advantage over MDI) and have a vapor pressure higher than TDI (hence it""s higher molecular weight structure). Surprisingly, such a foam also exhibited improvement in foam properties.
Foams of varying hardness, reasonable physical properties and good humid aged compression sets can be formulated with the present tetralin isocyanates. Physical properties such as elongation and tear were improved.
The present invention relates to isocyanates corresponding to the formula: 
wherein
n is a number from 1 to 2.
The present invention relates to isocyanates corresponding to the formula: 
wherein n is 1 or 2.
When n=1, the isocyanate can be 2- or 3-tetralin isocyanate. When n=2, the isocyanate can be 2,3-tetralin diisocyanate, 2,4-tetralin diisocyanate, 3,4-tetralin diisocyanate, 2,5-tetralin diisocyanate, or mixtures thereof.
The novel isocyanates of the present invention are produced by reacting tetralindiamine with phosgene. The starting diamines can be produced by processes already known (See xe2x80x9cNitrobenzene and Nitrotoluenesxe2x80x9d, Kirk-Othmer Encyclopedia of Chemical Technology, 4th ed, vol 17, 1996 and xe2x80x9cDiaminotoluenesxe2x80x9d, ibid, vol 2, 1992.). For example, tetrahydronaphthalene (tetralin) can be converted to the diamine by catalytic hydrogenation. In particular, the reaction of tetralin with nitric acid results in dinitrotetralin, which then is catalytically hydrogenated to give tetralindiamine.
Tetrahydronaphthalene is a commercially available product, which can be made by partially hydrogenating naphthalene.
The above-diamine is converted to the isocyanate of the present invention by reacting it with phosgene. Phosgene may be employed in either liquid or gaseous form, preferably liquid form. The tetralindiamine is dissolved in a mixture of diglyme/1,2-dichlorobenzene and added to the phosgene solution. The temperature of the reaction medium ranges from about 90 to 190xc2x0 C., preferably from 110 to 170xc2x0 C.
The tetralin di or isocyanate can also be made from the amine using phosgene free approaches such as urethane splitting.
The novel isocyanate of the present invention may be used in the same fields as aromatic polyisocyanates of prior art have been used. For example, it can be used in the fields such as polyurethane by reacting various compounds, including polymers, containing active hydrogen groups such as polyols, as well as intermediates, for producing other novel compounds or polymers, and so on. The new isocyanates according to the present invention may be used instead of TDI and/or MDI in all processes for the production of polyurethanes using these known polyisocyanates.